Communication sxstem



Dec. 15, 1953 R. A. CLARK, JR

COMMUNICATION SYSTEM 4 sheets-sha1' 1 Original Filed June 10, 1944 INVENTOR.

- ROBERT A GLARKLJR zer-.gm

ATTORNEYS Dec. V15, 1953 R. A. CLARK, .JR Re- 23,751

' COMMUNICATION SYSTEM Original Filed June l0, 1944 4 Sheets-Sheet 2 l 2nj coUPLmGA NETWORK MICROPHONE IN V EN TOR.

ROBERT A. CLARK JR.

BY l i MZ/:LJLVMM lATTOR N E YS 4 Shouts-.Sheet 5 6N. x AS R. A.ACLARK, JR

COMMUNICATION SYSTEM Dec. 15, 1953 original Filed June 10, 1944 m. N mm 1M M o v R T L O M C T V A M .Qa w. r R n En.: o ww 22m .R M v.. B A om 28Go 5 we: .6528 M .Qu

Re.l 23,751

De c. 15, 1953 R. A. CLARK, JR

COMMUNICATION sys'ru Original Filed June 10, 1944 4 Sheets-Sheet 4 INVENTOR ROBERT A. CLARK .m

BY MLM m v ATTORNEYS on mmmf.

en a @05u55 JUMP-ll' mm zwijn-24 Reissued Dec. 15, 1953 Ulxllllao- .v sTArEs PATENT OFFICE COMMUNICATION "SYSTEM Rohert. A. Glark, Jr., Chicago, ll l lr.` Originaly No. 2,393,291, dated January 22, 1946,@

SerialNfL539,672,1`J1le 1l),` 1944; "CApplica'tion: for reissue .april 24,1'1952, Serial No. `284,121 i 30 Qlaiins v(Cl.'1fl9 82 L Matter enclosed in heavy -bracketsll `appears in the orignalsp'atent 'but forms.' no part'.v of. this 1 reissue specification: matter printed indicatesltlle additions made-by reissue.

moving' along a predetermined route.'

Two-way space comm'unicationibetw'een a moving vehicle, such-,-`iorexample, as al train, mov-f` ing along a `f`1xed-route`and one or lmore stations l located along the route i's'of 1cem'parativelyrecent 1 origin. -lt is recognized that in sucha system the {rafnge of space-communication must-necessarilygjbe'restricted 'inv order to minimize interference with longrange radiotransmission on assigned `frequency channels. In -at least one proposed systenmthis' has kbeen accomplished lby employing -induetive coupling between the `vehicle st ationja'ndjthe way station toprovide signal f carrierienergy 'transfer Vbetween Y* the stations.'v

The usual system arrangementoi this character; hotveveigf makes no 'provisions fioriin anyjv'vay utilizing the 'communicating o'r Asignaling 'lacilitiesvvhich may parallel the vehicle*route in es" tablishing' communication channels between the-` vehicle station andthe various p'oints` alongT vthe f' 25 tion'ally paralleled Jby telephone communication routel YThus vthe usualrailwa'yjline convene facilities f between, one or more centrally locatedv` dispatcher stations and control towers or Way'j stations'spaced'along theli'n'e. Such railway`Y` lines are also usually' paralleled by telegraph and' power lines, yet theseffacilities a're'not normally used in establishing communication hannelsbetween the Vehicle stations, the way Astations,"and;

the v` d is1';`atcher stationor stations".

Itis an objectfoi the present inv'ention', `therelj fore, to providefa systemior communicating be- 1 tween' a vehicle proceeding along ajpredetfe'rmined`-.,

route and one or vmore stationsof xed location along t he 1oute which effectivelyfutilizestothe?? best` possible@ Aadvantage existing communicating;

ItL is' another object 'of the invention to provide an improved systemoi they` characteijdescrilcied j Whichmay beemployed tofurnish ttvo-Waycoinmunication between a'f'vehicle station and aidis-Q patcher. or master. station'y over channels which" respectively' include different ,way vstations located. along the route', over which vehicleis tI travelling,A

Accordingjto a further object ofthe invention;

thevehicle and way stations are each equippedw'l with' space communication equipment 'Qi 1ii`n`ited" communication range'," and the way stat ions are so spacedalong the routey thata substantial overj- 1 lap" is "provided between thev communication rangesof adjacent way st'ationsvvherebythe vehicle' station, is4 successively 'move d into the ranges of communication of successively adjacent wayfstations'as the vehicle proceeds f alongl predeterminedtrav'el route;

According to yet another object of the invention,A the vspace communication .equipment at the 5 Q various Way'stationsiscommonlycoupled `to a singlefsignal' radiating and pick-up line .paral-J/ leling.;thevehicleroute. Y

In accordance .witha still further :object .of the invention ai commongeneral purpose cominuni-vf cation.l channelis utilized'to interconnect :the dispatcheror master! vstation with the differ-'ent waystations, andeach Way station .includes fa-I oilitiesselectively controllable over thecommon channel for ioperatively associating.' `the space* communication equipment therea-t with the com-J monchanne'l 1forl the radiation of masterstation originated i signals at the lvehicle stationrand the .'w relaying of vehicle station originated.signals` to the fma'sterstation.

Accordingto still anotherlobject. of the-inven- I tion, eachlway stationvis alsoprovided' with fia-f i: cilties controllable from the -masterstationover .the 'commonchannelforselectively reversing` the direction infwhicli signals maybe transmitted be- .-I Y

tween `themaster station and the vehicle-i station More generallyfit is" an object'of thepresent-n invention to provide an-improvedsystemof the* character desem-bed Which Y includesrv relativelyI simpleand leasilyfoperable facilities -for providingcommunication between avehiclestation and any onejofa number'of waystations or a dispatcherl station. The"l invention; both as to its organization and method o f operatiom together Withiurthe'r ob=" jects and advantages thereof,` will bestbe unde'rstood by vreferenceto thejspecication taken in connection with 'the accompanying drawings-in' whichftf i Fig'.l 1 diagrammatically illustrates an improved communication system characterized by theY fea# j tures ofthe present invention; I f

Figzscheimatically illus-trates "the vehicle sta# tion equipment-'Which may e utilized-in the sysitem shoWn'infFig:1;'and7'" i Figs. 3V and '1iwhen laid endto end inthe order named illustrate the details 'of' the equipment pro-.j Vided'atone of the lWay stations includedin the* f' system shown in Figi-"1.

Referring-now" to' th'edrawings and more -particularly. to Figi-1l. thereof, the;communication;y system. there .schematically illustrated is. utilized 1" to provide for voicesigna'l transmission ibetween"' "s a dispatcherl station 'l5 and-.any vone'of aplu'- ralityiof tower or Way',.stations"'liu'iI itl, '13, LI-9, :.2

etc., located at spaced points along a. railway 3 track system III. It is also used to provide for voice signal transmission between any one of the named stations and the vehicle stations Iia, IIb, I2a and I2b of two trains II and I2 which may be moving in the same or different directions along the track system I0. As indicated by the dash line rectangles, each train moving along the track I may be equipped with at least two vehicle stations. These stations may be utilized for intratrain space communication or for communication between the stations of two different trains moving in the same or opposite directions along the track system, and the two stations of each train are usually provided in the engineers cab and the caboose or last car of the train. In accordance with conventional practice, the track system I6 is paralleled by a line I3, which is insulated from ground and may, for example, be used for power transmission or telegraphic signaling purposes.y This line is commonly associated with the various way stations to function as a signal radiating and pick-up circuit by means of which voice signals modulated upon an appropriate carrier may be transmitted in either direction between the various way stations and the vehicle stations of trains moving along the track system I0. In order to provide for telephone communication between the dispatcher station I and the various way stations I6, l1, I8, I3, etc., these way stations are also commonly associated with the dispatcher station by means of a two-conductor telephone line I4. Each way station is provided with a telephone subset which is bridged across the line I4.

Briefly considered, theequipment provided at the dispatcher station I5 comprises a telephone substation circuit 32, facilities for selectively seizing and operatively associating the different way stations with the common signal channel I4, and a press-to talk key :34 for controlling the equipment provided at a selected way station to condition the same for the radiation of voice signals originating at the dispatcher station. The substation circuit 32 may be of any conventional form although preferably is of the well-known antiside tone type conventionally utilized at telephone substations. In lieu of a handset, it preferably employs a loud speaker and microphone as the reproducing and transmitting elements. The selective calling facilities include a plurality of oscillators 20, 2|, 22 and 23, individually corresponding to the way stations I6, I1, I8 and I9, and the output voltages of which may be selectively impressed across the conductors of the line I4. Relays `28, 29, and 3I, arranged for selective energization by means of associated keys 24, 25, 26 and 21, are provided for selectively connecting the output terminals of the four identiiied oscillators across the conductors of the line I4. Current for energizing the enumerated relays may be derivedfrom the usual storage battery of appropriate voltage.

In order that the call signal receiving channel. respectively provided at the way stations I6, I1, etc., and of the specific character described below, may distinguish between voice signals and call signals transmitted over the line I4, the oscillators 20, 2|, 22 and 23 are adjusted to have output frequencies above the frequency range normally utilized for voice signal transmission over the line I4. Thus the voice signal transmission frequency range may be limited not to exceed an upper frequency limit of 3,000 cycles, in which case the oscillators may have output frequencies of 3,500 cycles, 3,750 cycles, 4,000 cycles and 4,250

4 cycles, respectively. This frequency spacing between the output frequencies of the oscillators is entirely adequate for reliable selective response of the call relays respectively provided at the way stations.

Referring now more particularly to the various way stations, it is pointed out that the equipment provided at these stations is of identical arrangement. Accordingly, only that located at the way station I8 has been illustrated in detail. In brief, the equipment at this station comprises a space signal transmitter 48, a space signal receiver 49, a call signal receiving channel 51, a call signal rectifier 62, a loud speak-er 65, a microphone or transmitter 64 of the sound powered type, and a relay network controllable in fthe manner described below to perform the switching operations which are required in utilizing the de'- scribed equipment to communicate between the dispatcher station or a vehicle station, or to rela-y signals between a vehicle station and the dispatcher station. More specifically, the transmitter 48 comprises an audio amplifier stage 50 and a carrier producing oscillator 52, both working into a modulator stage 5 I the output of which. may be impressed between the line I3 and ground through the contacts of a switching relay RI I0 and an app-ropriate coupling network 58. The receiver 49 is comprised of a two-stage signal modulated carrier amplifier 53 having its input circuit normally coupled to the line I3 and ground through the contacts of a switching relay RI I0 and the coupling network 5E, and its output circuit coupled to ythe input side of a detector and automatic volume control stage 54, the output terminals of which are coupled tol the 4input circuit of a power amplifier 55. Since the transmittei` 48 and receiver 49 are substantially conventional in circuit arrangement, the individual circuit elements thereof have not been specifically identified in the drawings. Also, the coupling network 56, through which signal voltages may be transmitted in either direction between the line i3, the transmitter 48 and the receiver 49,. may be of various conventional arrangements depending upon the particular character of the line I3. Regardless of its character, however, this coupling network is arranged to exclude from the transmitter 48 and the receiver 49, the voltages, appearing on the line lf3 in the. normal use;

thereof, and is also arranged to provide high irn-I pedance paths between this line and ground at the frequencies of the currents traversing the line. in the normal use thereof.

For the purpose of utilizing `the described equipment at the way station I8v to permit a vehicle station operator ito monitor the common line I4 and to then audibly call the attendant at the dispatcher station l5 if the line is idle, three relays RISE), RIM) and RI50 are provided at lthis way station. These relays are arranged to be energized by transmitting a call signal through the receiver 49 to a call signal rectifier network 62, the equipment provided in the latter network being identical with that included in the channel 51. The input side of this network is coupled to the output side of the power amplifier 55 through a. voice frequency blocking filter [56] 56a of conventional design. This filter is arranged to pass the call signal, which may be radiated at a frequency of 3,250 cycles, for example, outside of the band utilized for voice transmission. Facilities including a blocking lter [51] 57a may be provided at the output side of the amplifier 55 for preventing this call signal from being impressed channel 51,-utilized--in seizing-the way station -Iv from fthe dispatcher sltation-A- I 5,y `comprises a -one or-two section band pass-lterfSm-a call-vv signal amplifier 59,'a detector 60 --and av control tube 6I connectedin tandem in the-order named between` the line I4 and a -call--relayR-IIlllf-'f-Theloand pass filter 58 is preferably sharplytu-nedto 4-passonly a received-signal of 4,060 cycles-,- thereby excludingfrom the-succeeding stages-of -the channel 51 `the callr signa-1s corresponding-tothe# other way-staftions as well as-voice signals which-may loe-'transmitted over-the-line I4. In this regard-,it is notedI that the'correspondin'g-filters as providedat the other `way stationsl are respectively tuned-to `ipass only `frequencies of 3,5Q0cycles; 3,750 cycles and 4,2501cycles, whereby the* stations-may -only beseized when-the respective corresponding keys 24,-= 25 "and-'21 are operated-at the- -dispatcherstation-- Inaddition-,to the equipment thus'fardescr-ibed,--

the way station I8 is also-equipped With-1a dis---v patcher station call key I 24 and a switching relay- RI-2,"arranged for-selective energizationthrough then contacts of a press-to talk key- 66,-v which is utilized selectively to associate the transmitter -48 andthe-receiverg with the line- I 3.- Voice-signals are repeated from -the line I4 yto the transmitter 48 Iandfrom the receiver 49 to the line4 I4 through a coupling transformer M63 having a winding-53h bridged'across-'the2 conductors of this line. The way-station is further-provided with adirect current source. notshown,` of-appropriate voltage havinga positiveterminal connected to ground relayiterminals identinedby the negative polarity sign.;` lThis source is also /utlized to supply current to the cathode heaters-of thetubes embodied inthe; units 51,"62,-48 and III. f-Anode voltages vare and a'negativeterminal connected to all of the supplied to these Ytubes-from a 125 Volt directcurrent source, the negative-terminal of which is grounded-and the positive-,terminal-of whichis connected `to the conductor I26.

The vehiclevstations -I Ia, IIb; Illafib, etc.-, arcequippedwith space commi-inicat-ion- -equipmentof identical arrangement. In-brief; the 4equipment provided at'theyvehicle-'station IIa-comprises'a microphone vII-anda loud-speaker 40 which may beselectivelyassociated witha signal-pickupA and radiating-'circuit -36 through-a signal modulated carrier receiver- 38 and a ySignal-- modulated ,carrier transmitter-A 39, 4respectively.-- Morespecically; -the input terminals of the receiver'38 are normally associated-with the signal radiatingandy pickup circuit 36 through a couplingnetworkl and-the contacts of the switch-"-V ing. relay v45: The outputterminals -of thetrans mittler-3Sare also'adapted tobe coupled to the signal pickup and-radiating circuit. 36 through thejjcontacts lof the -switching relay 45A and the couplingnetwork Y3l. The receiver---fand transmitter 39 maycorrespond-precisely-in circuitarrangement to the receiver 49 and -transof fthe(` switching relay 45,--'together with; facilities for modulating the carrier output of the transmitter 39twith-a way station call signal.

These facilities; comprise a signal oscillator- 42H having an output frequency which corresponds to thev tuning of the filter [56] 56av and the filtersection providedgin the call signal rectiner-62 of thejillustrated-way station I8, i. e.,yof the order-- of 3250 -cycles.v Morespecificallm-the output- `mitter 48, respectively, of the equipment provided at'way station I8.v The-vehicle station equipment further comprises a press-to talk-,key 44 for-selectively controlling the energ-ization tive terminal. -of the .relay v45, .-;respectively-,. ai'

vacter` described. by 1L. 1 G'. Grondahlv and .P.fN..=f

6 terminals 'of the.v oscillator 42 are coupled., to fthe.- input side of the transmittergzthrough -a cou pling condenser, [481 .48m-and: this oscillator is arranged for selective .operationunderthe con-f -trol of a call key 43 having contacts .foralso conm.. trolling .the switching relay 45.- .Suitable.current;- supply..l facilities, including-a -battery..or other current source'y having .its positive and ,negative v. terminals.k connected.- to ground and. .to the. nega provided-for:supplyingl currents to the..var-ious1-. elements of the. described. vehicle station equip.- ment.

As indicated. above, the 'radius of spacev transf; mission from any .one-.of the; .-.Vehicle and. ,-way, 11; stations must .necessarily "be` restricted in order.; not to interfere with -.radio1 communication .upon assigned .frequency channels.. To Ithisfuend, p

straight-inductive coupling :of the.l general char Bossart.v in Railway --Signa1ing?-4 vfor December: 1943, starting .at page-685, is preferably. utilized between the signal pickup and-.radiating circuits',-v 36 individual to the vehiclestations and the. line-if..

.ground radiating and pickup circuit common.- to.

the -several waf,f..stationsl vA1so,.the"pickup.and radiating circuits 36 "individual..tof.the-.various-. vehicle -stationsare-.preferablyl of .the general character described in thisxarticle. With-@this arrangement,. the .range of transmission from.` each vehicle station is '-of.:courseedennitelysrefY,... stricted` to a short -distance,-..which. -may-Hvary-w within limi-ts depending-.uponr-thel power. output. of the transmitter 39.11 Another importants; factor which must be considered,.particularly the spacing of the waystations-.I I'I, etc., along.- the route followed. by wtherailway .track systemv I0 is Athe signal..attenuation-along the line-4.3;".l In this regard, Ait will be understood that the dis-,M

.- `tance between-.thisline and the vehicle station..

of a train. travelinga1ong-thei track-system. .III 1 may be very short, not exceeding a fewhundred yards, such that-the` spacci-ink .of a signal. channel between the .vehicle station-.andone ofthe way stations -is relatively-short. The-fonduetiveportion 4of the .channel may,--onthe other... hand, be relatively. long--dependingupon the-dise tance separating the. vehicle station-from. the way.- station.. It is the Aattenuation-in the .conductivei portions of `such signal channelswhich. must be. .s considered in -eletermining-the spacing-.between-` the way stations; Inaccordance--with one-.fea-

ture of the present -inven-tionthe way-stations'.` are so spaced valong-the route.fo1lowed.` bythe'.

f track system I8 that-:100 percentoverlapis pro-.1-

vided between the signal pickup.. and radiating.; rangesof vadjacent waystations...Thus, with.x the transmitters 39 and ll8-of-the-vehicle and-Way.- stations -set to .produce-tsignals-'of given .-.ield.-1 strength, the signalipiokup-and radiating range of the way-stationy I8,- for-exampley--in respect to a vehicle-station Awhich -is being .moved .along-the tracksystem IB, completely overlapsv the; corre---. sponding` ranges of the .two adjacent-way sta-- .tions- I'I and I9. Entirelylsatisfactory communi-.'

cations-between the lway .stations and .vehicles-- travelling .along 4the track system IU may .be .ob-1 tained .by utilizing a spacing-.of f from.25 to 50u-A miles between the adjacent way stations- From the above vdescription ofthe system,--itv will be understood that the space communication. equipment provided. .at the vehicle. stationv IIal may be utilized-by the-attendant at this-station to communicate-with the-attendant at .thepsta- 'tion IIb on the same train or with' either of thestations I2a and I2b of another train travelling along the track system in proximity to the train II. Thus, if the attendant at the station IIa desires to converse with the attendant at the station IIb, he may operate the press-to talk key 44 to complete an obvious circuit for energizing the switching relay 45. This relay, in operating, opens its contacts 45 to disconnect the input terminals of the receiver 38 from the coupling network 31 and closes its contacts 41 to connect the output terminals of the transmitter 39 to the pickup and radiating circuit 35 through the coupling network 31. After the relay 45 has thus operated, the attendant at the station IIa may speak into the microphone 4I thereby to eiect radiation of a voice modulated carrier by the radiating and pickup circuit 3G. rihis signal is picked up by the circuit 36 provided at the vehicle station IIb, and is transmitted through the coupling network 31 and receiver 38 of this station to the associated loud speaker 40 for reproduction. After the attendant at station ila has completed his statement to the attendant at the station I Ib, he may release the key 44 in order to condition the equipment at the station I Ia for the reception and reproduction of the reply transmitted from the called station IIb. Incident to the release of the key 44, the relay 45 is deenergized. In releasing, this relay opens its contacts 41 and closes its contacts 4S, thereby to disconnect the transmitter 3s from the coupling network 31 and to establish a channel for transmitting the reply signal to the input side of the receiver 38. It will be thus understood that through selective actuation of the press-to talk keys 44 respectively provided at the two stations I Ia and I Ib, a two-way conversation may be held between the attendants at these two statons. Space communication may be carried on between the vehicle station IIa and the vehicle station I2a, for example, of the train I2 in exactly the same manner.

ntratrain communication or intertrain communication effected through the use of the vehicle station equipment in the manner just explained, may be monitored at the way stations within the radius of transmission of the vehicle stations involved in such communication. Thus, if the train II is travelling along the track I8 within the radius of reception of the way station I8 at the time the facilities of thetwo stations IIa and I Ib are being utilized in communicating between these vehicle stations, the signals radiated from these stations are picked up by the common pickup and radiating circuit I3 and are transmitted through the coupling network 56 and the contacts I I I of the switching relay RI I8 to the input side of the receiver B9. In this receiver, the voice modulated carrier is amplified through the twostage ampliiier 53 and detected in the detector and A. V. C. stage 54, following which the voice frequency components of the signal are amplified in the power amplifier stage 55 and delivered through the lter network [51] 57a and the contacts |22 of the switching relay RIii to the loud speaker 65 for reproduction. At this point it is noted that the A. V. C. circuit embodied in the receiver 49 is of substantially conventional arrangement, and functions to vary the gain through the amplier 53 inversely in accordance with the strength of the received signal carrier, whereby the volume of the reproduced signal is maintained substantially constant regardless of the strength of the carrier appearing at the ,input side of the receiver,

It will thus be apparent that as the train Il, for example, moves along the track system I8, it is successively moved into the ranges of reception of the various way stations I8, I1, I6, etc., so that communication between the attendants at the stations IIa and IIb may be successively monitored by the attendants at the different way stations. It will also be understood that the attendant at the vehicle station IIa, for example, may converse directly with the attendant at any way station within the radius of transmission of the vehicle station by the simple expedient of calling this way station directly. Thus, if the attendant at the way station I I desires to converse with the attendant at the way station I8 While the train II is traveling within the range of communication between-these two stations, he may simply throw the press-to talk key [48] 44 to the talk position and call the way station I8, either by name or number. To reply, it is necessary for the attendant at the called way station I8 to actuate the non-locking press-to talk key S8, thereby to complete an obvious circuit for energizing the switching relay RI28. In operating, this relay closes its contacts I23 to complete an obvious circuit for energizing the associated switching relay RII8. At its contacts |22, the relay RIZII opens the connection between the loud speaker G5 and the output circuit of the receiver 49. At n its contacts I2I, the relay RI2I! completes an obvious path for bridging the microphone 34 across the input circuit or the transmitter 48.

The relay RI l), upon operating, opens its contacts llt to interrupt the path over which anode potential is normally supplied to the four tubes of the receiver 49, thereby to render this receiver inactive. At its contacts I I5, the relay RI I8 completes an obvious path for impressing positive anode potential upon the anodes of the three tubes included in the transmitter 48, thus rendering this transmitter active. At its contacts II4, the relay RI III opens the path over which voice signals may be transmitted from the line I4 to the loud speaker and the input circuit of the transmitter 48, At its contacts II3, the relay RI I0 prepares a path for transmitting voice signals from the microphone 64 to the line I4. At its contacts III, the relay RI Iopens the connection between the coupling network 56 and the input terminals of the receiver 4g. At its contacts II2, the relay RI IIJ connects the coupling network to the output terminals of the transmitter 43. Thus, the equipment provided at the way station I8 is conditioned for the radiation of voice modulated carrier signals to the vehicle station I ia. More specifically, when the contacts II5 of the relay RI Ii] are closed to apply an operating potential to the anode of the oscillator 52, operation of this oscillator to generate a high-frequency signal carrier is initiated. thereafter and when the attendant at the station I8 speaks into the Eloud speaker 65] microphone 64, the generated voice signal is amplified through the amplifier 50 and modulated upon the generated signal carrier in the modulator stage 5I. The voice modulated signal carrier appearing at the output side of the modulator 5I is impressed between the line I3 and ground through the contacts II2 and the coupling network 5S for radiation to the pickup and radiating circuit 36 of the vehicle station Ha. At this point, it lis specifically noted that the voice signals generated through operationv of the microphone 64 in the manner just explained are not impressed upon the line I4. Thus, with only the two relays BI Ii] l fand R120- operated-thecircuit-"over which vvoice signals-mayI be transmitted wfrom-:the.-n'licrophone 64 to the-unewl-aishelaopen ambetant-acts- Inl,

|52 and" |42A 'of-thethree -de-energized relays [RI-I0] R100 and RIM). I-t is also noted that -the v voice signals `.which are radiated from the vehicle station I Ia--and transmitted through thefreceiver 49 to the loud speaker S55-'for reproduc- -tion during a period -when the-two* relays` RI il) relayed `to the-line |4.- -Undersuch circumstances,

f the connection =-betWeen1the outputrter-minals of --the receiver 49 and theline I4 is also-.held open After the attendant -at =the way-station.- H3y has completed his replyto-theattendant-at-:the 'vehi- --cle station' I I a, lhe may. release ther self-restoring press-to'talkkey Hdl/[64], thereby to-fccndition Y .-theassociated equipment-for the reproduction of i.-thevoice--signals-which may be'fradiated from the station' 1I Ia in response to his reply-.f-"Incident to the release of the key (iB-,Athe-two" relays RIZU and f R'I IIJ 'are successivelyv cle-energized? in Vthe/ order fnamedf- Whenvthesefrelaysf-restore;"the trans" f' 1 mitter` is renderedff-inactive and the -receiver active, the' couplingnetwork 56 iS'sWitChed from a, connection with the transmitter-48 to aconnection with-the receiver- 48,the connection between thezmicrophone B4 and the-'transmitter 48" i is broken; and fthe co'nnection between ythe Iloud f' in ai manner -whichr-willt be fully'` apparent 'from the above: explanation.' Itwill thusbe' clear-'that V`Vthrough:selective Vactuation of lthe'presswo -talk 5 'keys 44 andBE respectivelyprovided at the Astations -I I-aand IB, a'ftwoewaycommunication may "be iheld z-betweenfthese1 two-"stationssodong as -zthe^"trai'n= II is "travelling within the-range of lcc'nn'm'unication extending to the way' station: |25.v

Assuming now that' the attendant atthe' vehi- 's clef station -I I er1-desiresL to converse withvv the 'dis- @patcher at the'statio'nf'l #the-'calli-toithefdispatchen-station may bevini-tiatedsby actuating '--the-'call key 431for. a' short-'interval-and'fthen releasing -the'same ."-When `this'ikey isactuated, ``the relay 45 is".energizedfthrouglifthecontacts "43h" and the'start circuit f for th'e-signal:r oscillator f 43 is' completed at1the'icontacts43af With-'the operating, afcarrier-modulated at th--callrrequency of the' oscillator 42 isfradiated-ffromthe l station I Ia. v Assuming'fthat thecall isfthusini- 'tfiatedwhilev th'e'train I-I istrave'lling within the 'range ofcommunication betweenlthe'fstations'-I Iav and ify I 8, the' modulated i'cairrierr. isi-transmitted 'through the 4re'ceiverMI and the filter' network'a received-1call-signal 'againsttr-ansmis'sion i to'. the .oud-speaker" G5.vl Similarly', the-filterfvl2561156a .has-'the' functionof 4preventing..signals-within Athe l'voicey frequency I range" from beingtransmitted tothe-'inputs'ide'ofthe-call signal rectifier-62.Tv It is-pointed out fur-ther: that a commoncallisignal r'equency,\l preferably of the forderof 3,25) cycles,

is Vassigned fori' calling any way' lstation from'l `any 'vehicle station: Inl-other words'.-the-:signal'oscil- Y-lators' 42 asllzirovided atv `all-vehicle'stations?"are f-set topperate at' thi's--frequencyg-ahd the".y filters [56] 5-6a'as-provided' at therespective 'way-fstations-- aredesigne'd to pass onlythisifrediienoy.

f The can #signallas-transmittedfthroughzth; n1- ="te"""[56]lf 56a' to*l the'- rectifier-"i '62- ist-rectified' r rl() [through this iiltery and is utilized] therein. to

eiect-a rise in the-current traversing theseries connected windings of the t'wo relays RISU- and RI 4,(2 of-sufiicient magnitude to cause these relays winding 'across' the output terminals of the receiver 49 [48]. The relay RIM., upon oper-ating,

. closes its contacts I3I -to shunt its own Winding withthe series connected-condenser |34 and re- .sisto'r -I35, thereby to render itself slow to release.

f Atits contactsl 32;- the relay RIM-completes an obvious circuit for energizing the slow to release i., relayk RIM.

Acloses its-contacts |52y to-shunt the contacts `I42 in-.vthecircuits for coupling the -line I4 tothe .The latter relay,-upon operating,

.,inputlsideof the transmitter 48 or the uoutput terminals of the receiver 49. At its contacts: I5I,

E' theirelay- RISO-prepares a circuit for energizing the switching relay RI I0.

" `'VS/'itlfl the three relays RIHL- RI40 and-R150 thus-operated, and-with the relay 45- operated at the vehicle -station -I Ia, a channelincluding Y the. transmitter-39', the contacts 4'I, the coupling network 31,- the space link between the stationsl Ia andIS'. the coupling network 56. the

receiver '49,' the contacts. II4`,"I42 and I52, -and ithe-coupling transformer'-BS, is provided for J--transmittingvoice` signals from the vehicle.y station .I laA to the line I4 and over-this line tothe -dispatcher station-for reproductionfy If, thereforefthe call is sufficiently urgent,- the' attendant wat the station IIa may l'callthe -dispatcherhy speaking -into the microphone 4I-a`nd identifying --the ytrain I Ijwithout waiting. tolinonitor the line Ain orderto-determine--the idle or busy condition v--thereol On-the. other hand, if the call -is not urgent, the normal procedure is for-the' attendantfat-theJstation-tomonitor the line. I4for a short monitoringperiod before actually calling the dispatcher. .To this-fend',l the key-'43h is released-,thereby to terminate the-transmission of --thencallfsignal from the-station IIa t'o the way -wstation I8 When `this signal isterminated, the `Vcurrent traversing the winding of the relay R14! is rapidly decreased to effectthe release offV this --relay YInf-restoring, the relay RMD opens its con- --tacts---I42-toA interrupt the shunt across the concompletes the` prepared circuit through the' con- Vtacts-Itil-'forenergizing.the switching relay RI I0.

- VlrEhe-relay RI IIJ, upon operating-opens its con- -i-tacts- I IIl tol interrupt the channel overl'which the --f-,sig-nal modulated-carrierwas delivered to the input-side ot-.the receiver 49.` Due. however, to

the- -describedl .slow to release characteristics of the -tWo Yrelays-R130 [RI-40] and RISO, these re- --1ays--stay operated v for several-seconds after the 'delivery ofthe call signal vvoltage to the'rectifier -62 -is--interruptedr- At its contactsl ll2gthe relay r -RI I0 'connects-the coupling -ne'twork 56 to the outputl terminals ofthe transmitter 48; thereby -tofprepare-theequipment-forthe radiation of voice-signals traversing the-line- I4.' At its Hcon- -l-tacts--II4,-therelay` [RIU] PR110- interrupts the -f path-bridgingthe-transformer winding 53a* across the'output side oit-the receiver-49. At its concontacts I IB, the relay RI Iii opens the circuit over which anode current is delivered to the tubes of the receiver 49, thus rendering this receiver inactive. At its contacts I I5, the relay RI It coil pletes the previously described circuit for delivering anode current to the tubes of the transmitter 48, thus rendering this transmitter operative. From the above explanation, it will be understood that upon operation of the switching relay RI I0, the receiver 49 is rendered inactive, and the transmitter 48 is rendered operative to radiate voice signals appearing upon the line I4 as a result of the use of this line in communicating between dispatcher station I and the other way or vehicle stations disposed along the track III. Thus if the line I4 is busy, the voice signals appearing thereon are impressed upon the input terminals of the transmitter 48 through the coupling transformer 63, the contacts |52, and the contacts II 3. Such voice signals are modulated upon the signal carrier generated through operation of the oscillator 52 and are delivered to the line I3 for radiation to the vehicle station I Ia through the contacts H2 and the coupling network 56. It will be apparent, therefore, that if the line I4 is busy at the time the call to the dispatcher station I5 is initiated at the vehicle station II, the attendant at this vehicle station may ascertain this fact during the short monitoring period which is determined by the release time of the relays RI3IJ and R150 [RIM] After a period of from ten to twenty seconds, starting with the operation of the relay RI IIJ, the relay R|30 is suiiiciently de-energized to releasel Upon restoring, this relay opens its contacts [|32] 131 to interrupt the path over which the delay impedances |34 and |35 are connected in shunt with its own windingy thereby to render itself fast to operate. At its contacts |32, the relay Rit@ deenergizes the relay RI5I1. The relay R-IES now restores and opens its contacts I5I to de-energize the switching relay RI I0.

At its contacts III and II2, the relay RIIIJ disconnects the line I3 from the output terminals of the transmitter 48 and reconnects this line to the input terminals of the receiver 49. At its contacts I|5 and IIS, the relay RI Il'I opens the circuit for delivering anode current to the tubes of the transmitter 48 and recloses the circuit for delivering anode current to the tubes of the receiver 49. Thus, the transmitter 48 is rendered inactive and the receiver 49 is endered active. At its contacts II3, the relay RIIll opens the described path for bridging the transformerv winding 53a across the input terminals of the ampliiier 5I?. At its contacts II4, the relay RI ID completes a path [through to the [closed] contacts |52 for preparing a circuit for bridging the transformer winding 63a across the output terminals of the receiver 45, Thus the equipment provided at the way station I8 is restored to normal.

If upon monitoring the line I4 in the manner just described the attendant at the vehicle station II a nds that the line is idle, he may then call the dispatcher at the station I5 by again pressing the key 43 and talking into the microphone 4|. When the key 43 is operated, the relays 45, RIBIJ. RIM) and RI function in the manner explained above to condition the equipment at the way station i8 for the relaying of voice signals from the station IIa to the line I4. Accordingly, the attendant may speak into the microphone 4| and identify the vehicle station Ila as a calling station at the dispatcher station I5. Upon release of the key 43, the relays RIED,

12 RI40 and RI50 function to first establish the described monitoring channel and to then restore the equipment at the way station I3 to normal.

From the above explanation it will be apparent that the described monitoring period is measured by the release time of the relays RIM! and RIEII. If desired, the two relays RI3I) and Rl may be of the dash-pot type, in order to provide for monitoring periods of longer duration than can be obtained by conventional slow-to-release relays. It will also be understood that since the three relays RI39, RIM andvRISIi, as respectively provided at the diiferent way stations, are arranged to respond to call signals of the same frequency, i. e., 3250 cycles, and the vehicle stations are equipped to transmit call signals of only this frequency, the equipment at two of the way stations may be concurrently operated in the exact manner described above when a call signal is radiated from a vehicle station. Thus if the station IIa is located at a point between the two way stations II and I8 at the time the abovedescribed call to the dispatcher station I5 is initiated thereat, the equipment at each of the two stations I8 and Il will be concurrently operated to establish two parallel monitoringT and call channels between the line I4 and the vehicle station IIa.

As indicated above, if the line I4 common to the several way stations is not busy at the time the above described call is initiated at the vehicle station IIa, the attendant at the latter station may audibly call the dispatcher attending the station I5 by speaking into the microphone 4I and identifying his particular vehicle station. The voice currents are modulated upon the carrier output of the transmitter 39 and radiated to the way station I8 where they are picked up by the receiver 49, demodulated in the detector 54, amplilied in the amplier 55 and transmitted through the coupling transformer E53 and over the line I4 for reproduction by the loud speaker at the dispatcher station I5. They are also delivered from the receiver output circuit through the contacts |22 to the loud speaker '55 for reproduction. Thus the attendant at the way station I8 is informed that the dispatcher is being called from the vehicle station I Ia. Knowing the identity of the vehicle station IIa, the dispatcher attending the station I5 may, by consulting train schedules, ascertain the approximate location of the train II along the track system i and thus be informed as to the proper way station to seize in order to establish a two-way communication channel between the dispatcher station and the calling vehicle station IIa. In the case under consideration, the dispatcher can readily ascertain that the way station I8 is within the range of communication with the vehicle station IIa. To seize this way station, the dispatcher may actuate the locking call key 26, thereby to energize the relay 30. This relay, in operating, bridges the output terminals of the 4000 cycle oscillator 22 across the conductors of the line I 4. The highfrequency voltage is passed through the lter 58 at the way station I8 and is impressed upon the input circuit of the amplifier 59. At each of the other way stations. the band pass lter 58 functions to prevent the described call signal voltage from appearing in the input circuit of the associated ampliers 5S. The signal voltage appearing at the output side of the illustrated filter 58 is amplified through the ampliiier 58, rectified in the detector BII, and the direct current component thereof is utilized to decrease the bias between t the-inputelectrodes'oi the' control tube Lthereby to increase the current-traversing the-Winding 'of' the call relay 'RIl'f' Thiscurrent, increase is f "s'u'cient tofcause the relayiRIUIJ temperate-1 At "ff #its contacts I Il I; the relay-RI 00 bridges` the trans- `for-mer.' winding 63a across the-outpu-tV-terminals 'of the receiver'- 49 fandprep'aresra" pathi -forbr-idg- "fling" this lWinding across `the 'input'f'terrninals of 'f tlfie-transniitter 48. 'At its contacts' '-I 02,' the relay @RIOB prepares af circuit for energizing*the-sWitch-- vingrela'y RI III. "Thefstation call-key 2.6 isfheld ir'rtsoii-normalv position to maintain theil'output 1' terminals of the oscillator'` 22- bridgedfacros'sfthe 'f conductors off-the line' I '4vfo'r the 'duration' ofthe f EVA'call to`v Vthe Vehicle station Ia. Substantially' concurrently `'with the operation ofy 'this keygthe "press-to talk-key 34 isi-'operated to'fcornplete. an obvious Epath for' connecting the negativefterminal of the battery 35 to the-f'lineic'onductors "f" -I 4af'and I4b through opp'r'asite'halves ofithetransf former winding' 133er?" "The yo'ltagethus applied tol the conductorsY ofthe line I41serves-to lenerv:gize-the'switchingrelay RI'ID in aacireuit''which Y'includes the conductors I4a and"=-I4b in parallel,

="and the 'contracts HD2.' In operating-tice.I relay RIvlprepares the equipment 'at the -wayfstation #i I8 fc'r the "radiationy of Voice lsignalsimpresse-cl A `upon. the. line I4- in a manner'Which-will befully 'apparent 'from thefprecedingexplanation.' f'Foll I if' lowing they operation of the twoi key's ZB'Ia'nd' 34 to effect the described switching operations at' the f Way station I8, the dispatcher 4attending tliestal, "tiori' I5 may speak into the microphone ortransmitter 'embodied-in 'the 'sub-'station equipment i #answered the' 'calli thej manner A r-just described, theke'yf34 may be restored tcncrrnal to-de-enertrainsmission of -voicesignals in-the'reverse directionyi. ei.,-f-ro'rn--thevehicle statior1'-I`I-a to'thedispatcherstation 32. To *initiate such voice trans-j myrn'ission; it 'is obviouslynecessary vfor the|` attend- "ant at ther *vehicle st'ation lI I a to actuate -`the press-to talk key 44i for the purpose of 'associating"thetransmitter-r 39l with" the pickup and: radi- """'ating-circuit 36. '-Morfr generally, it 4'Will'beap-f parent' from' the1 aloove-y `explanation 1 that v'bye-appropriate manipulation of the-press-totalk :keys "if 44 -andfl 34 'respectively' provided* at the two staftions IIafand I; Voice signalsmay be" transmitted inl'eithe'r' *direction*between'these*two stations over a communication channel "which1 in- ""'cludes'f-the Ispace'link betweenv the' station'f-I Ia 'andtheway 'station'l I!!1 and the wire link "conn'e'cting this 'way station; with" the' :dispatcher vsta- 'tio`r'1 I5." yThe' Voice signalsv originating' atthe' vehicl'e 'station are reproduced by the'lo'udY speaker 65v 'and'- serve to keep the attendant at" theway station-f I'tlI advised aste-the duraticn'o'f th'e'call. After the' convertation-fh'a'sbeeny concluded; the dispatcherli at' the' fr statiorif I Smayrreleasi :the

"thetw'o halves of the transformer Winding'63bf the'dispatcher 'statioif'il I5 lfrom being-reproduced f -by'the-lo'ud speaker IiE.v Aftrthedispatcherrhas conductors I4a and I4b, thereby to de-energize vr-open'sits contacts IUI vto'finte'rrupt-tlie paths 'over which thetran'sformer Winding 63a'1m'ay be selec- 'f` tively i bridged aerossth'e 'input terfn'ni'nals. 'f'f the ltrans'n'iitter' 48 or'r the outputlterminals of .theretion I8 is 7rest'oredto normal.

"The manner 1 inkl which "thev communication equipment"respectively provided at` the Votherytay 'stations vmay-#be seizedlon a. selective-Lbasis through selectiveoperation` ofthe callkeysl24, r2'5 and `2'I'- Willbe'evidentffrom the preceding rex- Y Y planation. It-Willfalsobe understood that if"-the dispatcher attending the kstation' I Sdesires 'toitalk with the attendant iatthewayfstation- I8;y for example, the-'callk'eyZG is' actuated tol-inipress'the 'conductors of the' line I4 and thus effect-'Loperation of thecaIlreIay-RIBUJ! Withithis'rela'y' operated 'and the two'relays iR I UUandiR'I 20 released,

1voice signals transmitted-'over the lin'e'l I'4'f'from the `dispatcher station l I5'lare` impressed lupon -Way station I4.` vThuslwith lonly-ith'e-relayl'REIIlII operated at the" s't'ationxll; thelpath'" for ftransrnittingv voice lsignals* from" the 'line' I4..v tol the transmitter? 48 is: heldf- 'open at" thelconlta'ct'siA I I 3.

A To answer'the' call;V it .isf necessary' for the" latits contacts'`l2f3fto energize the switchingffrelay RI I0. At its-'contacts I2I. and-5 I22-the relay f RIZ-@disconnectsthe-loud speaker' iiromlthe i 'transformerv Winding" 63"'andf prepares al-p'ath-'for bridging thev microphone f- E4 Y"across thisftransformer winding? The relay' R'I IIJ; in'- operating,

` lclose'sitscontacts'" I I3 to `co'nnectrthe 'microphone 54 across the transformer winding 63af' '-'Ilhe remaining 'circuit switching operations" of -th'e relay R'I I0 arewithout 'effectf Following'operation of viouslywb'e transmitted from the umicrophone 64 through'the transfornierVV BSand'cV'erth'e line I4 gi'ze'theswitching relay RI I0 'and thus prepare thefequiprnent` at 4the' -Way fstation'v IS--for--the the 'rela-ys lR'IZII and RI I0; voice-'signalsV :may obfor reproduction byf'th'e loudl speaker'` proi/ided at th'- dispatcher station' |51* It willfbe understood, therefore, tha-t -byv'sel'ective' actuation of y v4thepress-t'o talk key-EB-'at thecalledwayvstation larfvfsienals may' be transmitted inf'either directionbetwee'n theftwol stations I'Sandv I 8." In

this regard it'will bencted that With the-two=relays RI Ill and RI20 operated, the transmitter 48 isf' conditionedofor Voperation' fanti' IVoice signals the f 'vehicle lstation of any vehicle kmoving along thetrack systelh-I-'Ilfwithin the range of transmis- "sion'o'f'4v the wayV'stationv IBS? The attendant at any such' vehicle-station is thus informed that' the ffway1station" I8 is Ybusy. f lHere roaring-the release 'tion 'andwrelease of :the vcall relay: R-Iur 11n a manner entirely similar to that iust described, the dispatcher attending the station I5 may selectively call-the attendants at any one of the way stations IB, Il, I9, etc., associated with the line I 4.

It will be noted that when the equipment at the way station I8 is not in use on calls involving the dispatcher station I5, all of the relays provided thereat are deenergized. With the relays RIBU, RIE!) and RIM restored, the contacts lili, |52 and M2 are open to prevent voice signals from being transmitted from the line I4 to the loud speaker E5 or the input circuit of the transmitter 48 and to prevent voice signals from being transmitted from the output circuit of the receiver 49 or the microphone Gd to the line I Thus, the line I4 is guarded against receiving voice signals which might interfere with the use thereof by the dispatcher attending the dispatcher station l5. If the attendant at the way station I3, for example, desires to monitor the line i4 for the purpose of determining the idle or busy condition thereof, he may actnate the key i251 to bridge the loud speaker 55 and the input circuit of the transmitter 43 across the transformer winding 63a over a path which includes the contacts Ilil and the contacts |22. lvl/*ith this monitoring connection established, voice signals appearing upon the line I4 are obviously transmitted to the loud speaker 65 for reproduction. Il upon establishing this monitoring connection, the attendant at the way station I8 ascertains that the line I4 is idle, he may call the dispatcher station I5 by actuating the press-to talk key 68, thereby to effect the sequential operation of the two relays RIZD and RI 1B in the manner described above. With these two relays operated, the loud speaker 55 is disconnected from the transformer winding 63 and the microphone E4 is bridged across this winding to complete a channel over which voice signals may be transmitted to the dispatcher station I5 for reproduction. After instituting a call in the manner just described, the attendant at the way station I8 may, by selective operation of the key GE, condition the equipment at the way station i8 for the reception of signals received over the line i4 or the transmission of signals to this line, thereby to provide for a two-way communication with the dispatcher station I5. After the call is completed, the key I2 should be restored to normal in order to interrupt the minotoring connection between the loud speaker 55 and the line i4.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein which are within the true spirit and scope of the invention as defined in the appended claims.

I claim:

l. A system for communicating between a dispatcher station and a vehicle moving along a predetermined route, comprising way stations provided at spaced points along said route and each including space transmitting and receiving means, signal radiating and pickup means common to the transmitting and receiving means at said way stations, a station carried by said vehicle and including space transmitting and receiving means, a [signal] single two-way telephone channel commonly associating said way stations with said dispatcher station and constituting the sole means for such purpose, and means for selectively establishing communication channels between said dispatcher station and said vehicle station over routes which respectively include different ones of said way stations.

2. A system for communicating between a dispatcher station and a vehicle moving along a predetermined route, comprising way stations provided at spaced points along said route, a single two-way telephone channel commonly associating a dispatcher station with the way stations, a station on said vehicle, means providing for space communicating between said -vehicle station and different ones of said way stations when said vehicle is disposed at different points along said route, and means controllable solely by way of said telephone channel for selectively establishing communication channels between said dispatcher station and said vehicle station over routes which respectively include diierent ones of said way stations and all of which include said telephone channel.

3. A system for communicating between a dispatcher station and a vehicle moving along a predetermined route, comprising way stations provided at spaced points along said route, a single two-way telephone channel commonly associating the dispatcher station with the way stations, a station on said vehicle, means providing for space communication between said vehicle station and different ones of said way stations when said vehicle is disposed at different points along said route, means at said vehicle station for signaling said dispatcher station over different routes which respectively include the nearest ones of said way stations and all of which include said telephone channel as said vehicle moves along said predetermined route, and means at said dispatcher station controllable solely by way of said telephone channel for establishing communication channels between said dispatcher station and said vehicle station over routes which respectively include different ones of said way stations and all of which include said telephone channel.

4. A system for communicating between a dispatcher station and a vehicle moving along a predetermined route, comprising Way stations provided at spaced points along said route, a single two-way telephone channel commonly associating said dispatcher station with said way stations, a station on said vehicle, means providing for space communication between said vehicle station and different ones of said way stations when said Vehicle is disposed at diierent points along said route, means at said Way stations selectively controllable from said dispatcher station solely by way of said telephone channel for establishing one way communication channels between said dispatcher station and said vehicle station over routes which respectively include different ones of said way stations and all of 'which include said telephone channel, and means at the way station included in any one of said communication channels and controllable fromV at least one of the vehicle and dispatcher stationsior changing the direction in which signals may be transmitted over the communication channel.

5. A system for communicating between a dispatcher station and a vehicle moving along a predetermined route, comprising way stations provided at spaced points along said route, a single two-way telephone channel commonly associating the dispatcher station with the way stations, a station on said vehicle,` means providing for space communication between said vehicle station and dierent ones of said Way stations when said vehicle is disposed at different points along said route, means at said dispatcher station for selectively seizing saidway stations solely by way of said telephone channel to establish one way communication channels between said dispatcher station and said vehicle station over routes which commonly include said telephone channel, and means at any seized `o ne of said way stations controllable fromk said dispatcher station over said telephone channel for changing the direction of signal transmission over the established communication channel.

[6. A system for communicating between a dispatcher station and a vehicle moving along a predetermined routes comprising way stations provided at spacedpoints along said route, a station on said vehicle. said way stations and vehicle station eachincluding space communication equipment of limited predetermined communicating range in eitherdirecton along said route, said way stations being` so spaced along said route that the range. oi'. communication oi each way station substantially overlaps the range of communicationl of eachadiacent way station,l whereby said vehicle station is successively moved into the ranges oi?A communication of different pairs of said way stations as said vehicle p'roceeds along said route, and. means for selectively establishing communication channels between said dispatcher station and said vehicle station over routes which respectively include the Way station nearest or next nearest saidl vehicle] 7. A system for communicating with a vehicle moving. along a predetermined route, comprising a master station, a` plurality of way stations located at spaced points along said route, a single two-way telephone [signal] channel commonly associating said master station with said way stations, said way stations each including space communicating equipment for` radiating signals to a vehicle moving along. said. route andfor receiving signals radiated from the vehicle, and means controllable from said. master station [over said] solely by way of said telephone [signal] channel for selectively associating said way stations with said channel for the trans',- mission of signals between said master station and the space communicating equipment at any selected way stations' over said telephone channel.

8. A system for communicating with a vehicle moving along a predetermined route, comprising a master station, a pluralityof way stations located at spaced points along said route, a single two-way telephone [signal] channel commonly associating said master station with saidway stations, said way stations each including space communicating equipment for radiating signals to a vehicle moving along said route and. for receiving signals radiated from the vehicle, means controllable from said master station [over said] solely by way of said telephonel [signal] channel for selectively associating said way stations with` said channel for the transmission of signals in one direction by wail of said channel betweensaid master station andthe space communicating equipment of the selected way station, and meansy at the selected way station, [also] controllable over said [signal] channel, fori controlling the equipment at the selected. way station to change the direction in which signals may be transmitted between the master station andthe selected way station by way of'said. channel.

9. A system for communicating with a vehicle.l moving along a predetermined route, comprising a master station, a plurality of. way stations located at spaced' points' along said route, asignal channel commonly associating said master station with said way stations, said way stations each including space communicating equipment for radiating signals'received over said channel toa vehicle moving along said route and for relaying signals radiated from said vehicle to said channel, means at said master stationnior selectively transmitting control signals [over] solely by way of said channel having frequencies respectively corresponding to the diierent way. stations, and means at said way stations selectively responsive to said control signals of diierent frequencies for selectively associating said way stations with said channel for the transmission of signals between said master station and the space communicating equipment at any selected. way station.

lo. A- system. for communicating with a ve-i hcle moving along a predetermined route, comprising a lmaster station, aplurality of way stationsl located at spaced points along said route,- a two-conductor signal channel commonly associating said master station withsaid way stations;- said way stations each including space communicating equipment for radiating signals received over said channel to a vehicle moving. along said route and for relaying. signals radiated from said vehicle to said` channel, means at said master station for selectively transmitting control signals over said channel having frequencies respec tively corresponding to the diiierent way stations.- means at said Way stations selectively respon.- sive tosaid. control signals of d-iierent frequencies for selectively associating said way stations with said channel for the transmission of signals recel-ved by the equipment at the selected way station tol said master station over said channel, and means at the selected way station controllable. over the two conductors of said channel in parallel froml said master station for selectively conditioning the equipment at the se'- lected way station for the radiation of signals received over said channel from said master sta--l lon'.

1-1. A system for communicating with a vehicle moving along apre-determined route, comprising a master station,` a plurality of way stations located` at spaced points along said route; a signal. channel commonly associating said master station` with said way stations, said way stations each includingv space communicating'. equipment for radiating to a vehicle moving along said route signals having frequencies With-` in av predetermined' frequency band and received y over said signal channel andfor relaying signals` radiated from said vehicle to saidl channel`l means at: said master station for selectively transmitting control signals over said channel having frequencies outside said` predetermined frequency band and respectively corresponding toi thel dii--` ferent way stations, and means at said way stations selectively responsive to said control signals of diiierent frequencies for selectively associating said way stations' with said channel for thel transmissioncf signals between said` master`` station and the space communicating.'- equipment at any selected-way station.

12. A system for communicating with a ve# hicle moving along a. predetermined route, com'- prising amaster station, a plurality ciV way staf' tions located atspaced points along Said route', a' two-conductor signal channel commonly connec-ting said way stations withsaid master station, said` way stations each including space communi.-` cating equipment for: radiating to a vehicle mov-zl ing along said route signals having frequencies:

within a predetermined frequency band and received over said signal channel from said master station, and for relaying signals radiated from said vehicle to said channel, means at said master station for selectively transmitting control signals over said channel having frequencies outside said predetermined frequency band and respectively corresponding to the different way stations, means at said way stations selectively responsive to said control signals of dierent frequencies for selectively associating said way stations with said channel for the transmission of signals received by the equipment at the selected way station to said master station over said channel, and means at the selected Way station controllable over the two conductors of said channel in parallel for selectively conditioning the equipment at the selected way station for the radiation of signals received over said channel from said master station.

13. A system for communicating between a master station and a vehicle moving along a predetermined route, comprising a way station 1ocated along said route, a station on said vehicle, means at said vehicle and way stations providing a space communication link between said vehicle and way stations, a general purpose communication channel associating said master station with said way station, and means at said way station controllable over said space link from said vehicle station for permitting said communication channel to be monitored from said vehicle station over said space link.

14. A system for communicating between a master station and a vehicle moving along a predetermined route, comprising a way station located along said route, a station on said vehicle, means at said vehicle and Way stations providing a space communication link between said vehicle and way stations, a general purpose communication channel associating said master station with said way station, and means at said way station controllable over said space link from said vehicle station for establishing a calling connection between'said vehicle and master stations which includes said space link and over which a'call signal may be transmitted to said master station, and for then altering the connection to establish a monitoring connection between vehicle and way stations over which said communication channel may be monitored from said vehicle station.

l5. A system for communicating between a master station and a vehicle moving along a predetermined' route, comprising a way station located along said route. a station on said vehicle, means at said vehicle and way stations providing a space communication link between said vehicle and way stations, a general purpose communication channel associating said master station with said way station, means at said way station controllable over said space link from said vehicle station for establishing a calling connection between said vehicle and master stations which includes said space link `and over which a call signal may be transmitted to said master Station, and for then altering the connection to establish a monitoring connection between vehicle and way stations over which said communication channel may be monitored from said vehicle station, and means at said Way station controllable over said communication channel from said master station for establishing a communication connection between said master station `and said vehiclestation which includes said communication channel and space linkin series.

16. A system for communicating between a master station and a Vehicle moving along a predetermined route, comprising a way station located along said route, a station on said vehicle, space communication equipment at said vehicle and way stations providing a space communication link between said vehicle and way stations, a general purpose communication channel associating said master station with said way station, means at said vehicle station for transmitting a control signal to said way station over said space link, means at said way station responsive to said control signal for conditioning the equipment at said way station to relay signals radiated from said Vehicle station to said communication channel, thereby to permit call signals to be transmitted to said communication channel from said Vehicle station, and means operative following the operation of said last-named means for conditioning, for a period of limited duration, the

' equipment at said way station to relay signals received over said communication channel to said space link, whereby said communication channel may be monitored from said vehicle station.

17. A system for communicating between a master station and a vehicle moving along a predetermined route, comprising'a way/"station located along said route, a station on said Vehicle, space communication equipment at said vehicle and way stations providing a space communication link between said vehicle and way stations, a general purpose communication channel associating said master station with said way station, means at said vehicle station for .transmitting a control signal to said way station over said space link, means at said way station responsive to said control signal for conditioning the equipment at said way station to relay signals radiated from `Vsaid vehicle station to said communication channel, thereby to permit call signals to be transmitted to said communication channel from saidl vehicle station, means operative iollowing the operation of said last-named means for conditioning, for a period of limited duration, the equipment at said way station to relay signals over said space link from said communication channel, whereby said communication channel may be monitored from said vehicle station, and means at said way station controllable over said communication channel from said master station for establishing a communication connection between said master station and said Vehicle station which includes said communication channel and space link in series.

18. A system for communicating with a Vehicle moving along a predetermined route, comprising a dispatcher station,`a plurality of way sla-tions located at spaced points along said route, a station on said Vehicle, a single general purpose twovwire communication channel commonly associating said dispatcher station with said way stations, said way stations and said vehicle station each including space communicating equipment for radiating signals and receiving radiated signals, whereby different space communication links may be established between said vehicle station and different ones of said way stations, and means controllable from said dispatcher station [over] solely by way of said two-wire communication channel for selectively establishing communication channels between said dispatcher andA vehicle stations over routes which respec- 2.1' tively include different selected ones of said space links and all of which include said twowire channel.

19. A. system for communicating witha vehicle moving along a predetermined route, comprising ai dispatcher station, a pluralityv of way stations located at spaced p'ointsalongj said route, a station on said'vehicle, av general purpose communi'- cation channel commonly associating said dispatcher-station with saidI way stations.,` said Way stations and. said vehicle station each including space. communicating equipment for radiating signals and receiving' radiated signals, whereby different space communication links may lbe established between saidI Vehicle and way stations, means at each way station controllable over theassociated space link'from said vehicle station fin'1 permitting said communication channelA to be monitored :from` saidvehicle station over said associatedv space link, andL means controllable from said master station overl said' communication.' channel for 'selectively establishing communicationchannels between said dispatcher and vehicle stations over routes' which respectively includediiierent selected ones of said. space links.

20. A system for communicating between a master station and a vehicle moving along a predetermined route, comprising a way station located along said route, a station on said vehicle, space communication equipment at said vehicle 'and way stations providing a space com-munication link between said vehicle andway stations, a general purpose communication channel associating said master'station with saidway station, means at' said vehicle station for transmitting a control signal to said Way station over 'said space link; meansat said waystation responsive to said control' signal for conditioning the equipment at said way station to relaysignals radiated fromsaid vehicle station to said` communication channel, thereby to permit callvsignals to be transmitted tosaid communication channel from said vehicle station, and means responsive to the termination of said control signal-for conditioning the equipment at said way station to relay signals received over said communication channel'to said vehicle station whereby said communication channel maybe monitored from said-vehicle station.

21'. A system forv communicating between a dispatcher station and a vehicle movingv along a predetermined route, comprising way stations provided at spacedpoints along said route, a staon said vehicle,` means providing for space communication between said vehicle station and different ones of said way stations when said vehicle is disposed at dierent pointsalong said route, means for selectively establishing communication channels between said dispatcher station and said` vehicle station over routes which respectively include different ones of said way stations, and-means controllable from the vehicle station for'obtaining an indicationl at said vehicle station of the. busy or idlev conditionof the communication channels.

-22. A'sustem-for communicating between a dispatcher. stationA andi a vehicle lmoving. along apre'- d'eterminedroute, comprising way stations'pro'- vided at spaced pointsalong said route, a station on said vehicle, means providing for space communication between Asaid vehicle station and different ones of saidway stations when said vehicle is disposed at digerent points along said route, means atri saidlveh'icle station for signaling said dispatcher station over dierent routes which respectively., include the nearesty ones ofsaid'way stations as said vehicle moves along said predetermined route, means at said dispatcher station for establishing communication channels'bet'ween said dispatcher station and said vehicle station over routes which respectively include dierent ones of said way stations, andy meansV controllable from the vehicle' station for obtaining an indication at said vehicle station 0)" the busy or idle condition of the communication channels.

23'. A system ,for communicating between a dispatcher stationand a'vehicle moving along a predetermined route, comprisingv way stations provided at spaced points along said route, a station on said'vehicle, means'providingfrorspace communication between said vehicle station and different ones of said'way stations when said'vehicle is disposed at different points` along said route', means at said dispatcherstatitmv for selectively seizing said wayv stations' tov establish one way communication channels between said dispatcher station vand said vehicle station, means at any seized one of said'waystations controllable ,from said dispatcher station-for changing the direction of signal transmissionk over theestablished communication channel, andmeans controllable ,from the vehicle station for obtaining an indication at said vehicle station of the busy-or idle condition of the communication channels.

24; A system for 'communicating'with avehicle moving along a predetermined'route; comprising a master station, a plurality' of' way stations located at spaced'points alongsaid route; a single two-way telephone channel commonly associating said master station with said way Stations, said wayl stations each including space communicating equipment for radiating signals to avehi'cle moving along said route and for' receiving signals radiated from the vehicle, means controllable from said masterv station over said telephone channel for selectively associating said way stations with said channel for the'transmission of signals between said masterstation andthe space communicating equipment at' any selected waJ stations over said telephone channell andmeans at the vehicle station responsive to signals derived from at least one ofthe waz/'stations for obtaining an indication at said vehicle station ofthe busy or idle condition of said telephone signal channel.

25. A system for communicating with a vehicle moving along a predetermined route, comprising a master station, a plurality of way. stations located at spaced pointsalong said route, a single two-way telephone channel connecting said master station with each of said way stations, said way stations each including space communicating equipment for radiating signals to a vehicle moving along said route and ,for receivingsign'als radiated from the vehicle, means controllable from said master station solelyby way of said channel for selectively associating saidway stations with said channel for the transmission of signals in one direction by way of said channel between said master station andthe space communicating equipment ofth'e'selected way station, means at the selected way station, controllable -over said channel, for-controlling the equipment at the selected way station to change the direction in which signals maybe transmitted between the master station andthe selected `waysiation by way of said channel, and means at the vehicle station ,for obtainingV an indication at said vehicle station of the busy or idle condition of said channel.

26. A systemifor :c'ommunicatingwith a vehicle moving along a predetermined'route, comprising a dispatcher station, a plurality of way stations located at spaced points along said route, a station on said vehicle, a single two-way general purpose communication channel commonly connecting said dispatcher station with each of said way stations, said way stations and said vehicle station each including space communicating equipment forradiating signals and receiving radiated signals whereby digerent space communication links may be established between said vehicle station and different ones of said way stations, means controllable from said dispatcher station solely by way of said general purpose channel for selectively establishing communication channels between said dispatcher and vehicle stations over routes which respectively include different selected ones of said space links and commonly include said general purpose channel, and means at the vehicle station for obtaining an indication at said vehicle station of the busy or idle condition of said general purpose channel.

27. A system for communicating between a dispatcher station and a vehicle moving along a predetermined route, comprising way stations provided at spaced points along said route, a single two-way telephone channel commonly connecting said dispatcher station with each of said way stations, a station on said vehicle, means providing for two-way space communication between said vehicle station and different ones of said way stations when saidvehicle is disposed at different points along said route, means for selectively establishing communication channels between said dispatcher station and said vehicle station over routes which commonly include said telephone channel and respectively include different ones of said way stations, and means for producing an indication at said vehicle station representative of the busy or idle condition of said telephone channel.

28, A system for communicating between a dispatcher station and a vehicle moving along a predetermined route, comprising way stations provided at spaced points along said route, a single two-way telephone channel commonly connecting said dispatcher station with each of said way stations, a station on said vehicle, means providing for two-way space communication between said vehicle station and different ones of said way stations when said vehicle is disposed at dierent points along said route, means at said vehicle station for signaling said dispatcher station over different routes which respectively include the nearest ones of said way stations and commonly include said telephone channel, means controllable from said dispatcher station over said telephone channel for establishing communication channels between said dispatcher station and said vehicle station over routes which respectively include different ones of said way stations and commonly include said telephone channel, and means controllable from said vehicle station for determining the busy or idle conditionI of said telephone channel.

29. A system for communicating between a dispatcher station and a vehicle moving along a predetermined route, comprising way stations provided at spaced points along said route, a single two-way telephone channel commonly connecting the dispatcher station with each of said way stations, a station on said vehicle, means providing for space communication between said vehicle station and dierent ones of said way stations when said vehicle is disposed at different 24 a pointsalong said route, means at said waystations selectively controllable over the telephone channel ,from said dispatcher station for establishing one way communication channels between said dispatcher station and said vehicle stations over routes which respectively include different ones of said way stations and commonly include said telephone channel, means at the way station included in any one of said routes and controllable from at least one of the vehicles and dispatcher stations for changing the direction in which signals may be transmitted over the channel, and means at the vehicle station for providing an indication of the busy or idle condition of said telephone channel.

30. A system for communicating between a dispatcher station and a vehicle moving along a predetermined route, comprising way stations provided at spaced points along said route and each including space transmitting and receiving means, signal radiating and pickup means common to the transmitting and receiving means at said way stations, a station carried by said vehicle and including space transmitting and receiving means, a signal channel commonly associating said way stations with said dispatcher station, means on said vehicle for transmitting a distinctive control signal to the nearest one of said way stations, means in said one way station responsive to said control signal for conditioning the equipment at said one way station to relay signais radiated from said vehicle station to said signal channel, thereby to permit call signals to be transmitted to said signal channel, and means for selectively establishing communication channels between said dispatcher station and said vehicle station over routes which respectively include -diyerent ones of said way stations.

31. A system for communicating with a vehicle moving along apredetermined route, comprising a master station, a plurality of way stations located at spaced points along said route, a signal channel commonly associating said master station with said way stations, said way stations each including 'space communicating equipment for radiating signals received over said channel to a vehicle moving along said route and for relaying signals radiated Jfrom said vehicle to said channel, means on said vehicle for transmitting a distinctive control signal to the nearest one of said way stations, means in said one way station responsive to said control signal for conditioning the equipment at said one way station to relay signals radiated from said vehicle station to said signal channel, thereby to permit call signals to be transmitted to said signal channel, means at said master station for selectively transmitting control signals over said channel having frequencies respectively corresponding to the different way stations, and means at said way stations selectively responsive to said control signals of dierent frequencies for selectively associating said way stations with said channel for the transmission of signals between said 'master station and the space communicating equipment at any selected way station.

s ROBERT A. CLARK, JR.-

Name ADateA Gauthier Sept. 8, 1925 Number 

